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Abstract

Livestock manure is a valuable source of plant nutrients
for crop production in the Central Kenyan highlands but
its quality in terms of available nitrogen (N) is low due
to considerable N losses through ammonia volatilization.
This study aimed at assessing the potential of agroorganic
wastes to reduce N losses from manure heaps
during the storage period. Three organic amendments
selected from a laboratory simulation experiment were
evaluated under farmers’ conditions in Karura, Kiambu
District for their ability to reduce N losses from cattle
manure heaps. The effect of a polyethylene sheet
covering of manure heaps on N retention was also
determined. There were eight treatments that comprised
three agro-organic amendments (maize stover, coffee
pulp and sawdust) and the control, with or without a
polyethylene cover. Agronomic effectiveness of the
“treated” manure samples and N uptake by maize
seedlings was evaluated in a glasshouse experiment.
Total N content of manure amended with organic
materials ranged from 1.26 to 1.85%. The N in
manures with organic amendments at the start and at
the end of storage was significantly different (p ≤
0.05). Cumulative N loss ranged from 1.60 to 6.80 g
kg-1 depending on the type of amendment. Nitrogen
lost from non-amended manure was 2.74 g kg-1 with
polyethylene cover and 6.80 g kg-1 without the
polyethylene cover, which represented 19 and 46% of
the initial N respectively. Maize growth improved
significantly (p≤0.05) with increasing rates of manure
irrespective of the organic treatments except for
manure amended with sawdust. Treatments that
received the recommended rate of N at 100 kg N ha-1
had significantly higher (p≤0.05) biomass (21.55 g
plant-1) than the control which produced only 2.78
g/plant. Nitrogen uptake increased with increasing
rates of manure and was higher (p≤0.05) with manure
amended with coffee pulp. Covering manure heaps to
reduce moisture loss was also beneficial in reducing N
losses.